The Dental cosmos . E DENTAL COSMOS. It now becomes a question between safety and appearance, in whichthe limits of safety should be closely approached, but not over-stepped. Judgment as to the strength of the angle becomes espe-cially important. The apparent strength of the enamel is first to beconsidered. Excavations show it to be practically unsupported bydentine. In the illustration before us the triangular grooves e, eare plainly marked to and over the buccal ridge, and disappear onthe buccal surface by becoming shallower. The chances for strengthwould be much better if these grooves were
The Dental cosmos . E DENTAL COSMOS. It now becomes a question between safety and appearance, in whichthe limits of safety should be closely approached, but not over-stepped. Judgment as to the strength of the angle becomes espe-cially important. The apparent strength of the enamel is first to beconsidered. Excavations show it to be practically unsupported bydentine. In the illustration before us the triangular grooves e, eare plainly marked to and over the buccal ridge, and disappear onthe buccal surface by becoming shallower. The chances for strengthwould be much better if these grooves were not so marked. Anexamination of the denture generally shows the developmental groovesto be deep, and that there are a number of fissures. In this mouththe junctions of the enamel-plates are not strong ; therefore, in thiscase, the only safe course is to cut away the whole of the mesial mar-ginal ridge, and the angle to and over the buccal ridge onto the buccalsurface, as shown in Fig. 18. Fig. 17. Fig. 18. Fig. Fig. 17. Upper first bicuspid with cavity in the mesial surface, a, Buccal cusp ; b, Lingualcusp; c, Distal groove; d, Central groove; e, Triangular grooves, mesial and distal; f,f,Marginal ridges, mesial and distal; m, Carious cavity. Fig. 18. Same tooth as in Fig. 17, but with cavity prepared for filling, a, Mesio-buccal anglecut away to triangular groove ; b, Mesio-lingual angle cut away to a line that will be self-cleansing ; c, Shallow slot in the line of the central groove for anchorage; d, Line of contourof filling; e, Line of contour of the cuspid. The lines d and e show the form of proximatecontact. Fig. 19. The same teeth as in Fig. 18, after filling, in outline from the buccal surface, showingthe form of contact and the interproximate space. If, in a case otherwise similar, the developmental grooves are slightin the tooth itself, and also in the teeth of the denture generally, andif there are no fissures of the enamel, conditions showing that thejunction
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